Prop suggestion?

[Sean Janne]

I'm putting a CMB 45RS into a 39" mono hull. What would be a good sub surface prop?

 

[rumrunner]

X450/3 works great

 

[Kez]

It depends on how deep you run the prop. The deeper you run the prop the more load on the engine. I have a monos with sub-surface drive. I start with X447 and end up with X648 and X450. I have to raise the strut to turn the bigger prop though.

 

[Sean Janne]

It depends on how deep you run the prop. The deeper you run the prop the more load on the engine. I have a monos with sub-surface drive. I start with X447 and end up with X648 and X450. I have to raise the strut to turn the bigger prop though.

The center of the prop is about an inch below the keel. That's as high up as I can get it. The props you mentioned, are they 2 or 3 blade? I have a x450 2 blade that I used with my old K&B 7.5. Can I start with that, or is it too small?

 

[Kez]

It depends on how deep you run the prop. The deeper you run the prop the more load on the engine. I have a monos with sub-surface drive. I start with X447 and end up with X648 and X450. I have to raise the strut to turn the bigger prop though.

The center of the prop is about an inch below the keel. That's as high up as I can get it. The props you mentioned, are they 2 or 3 blade? I have a x450 2 blade that I used with my old K&B 7.5. Can I start with that, or is it too small?

1" below the keel is pretty deep. I started mine at 1/2" and my K&B 7.5 had problem handling the X450. My Picco 45 is happy with the X448 and even the X548 with the pipe at 10.25 to 10.5"

The props I mentioned are 2 blade. I don;t think Octura ever made a 3 blade 448 or 648. They make a 3 blade X450 as Shane has suggested.

 

[jeff baham]

pictures would help out on the new cmb45rs set-up ,if your strut do not go higher, you will have to file the slot of the strut down to make it come up. local hardware store have coarse rat tail files to make cutting easy

 

[Sean Janne]

Here's my drive set up:



As you can see, I can't raise it up any more without cutting the center part of the mount. Also, it kind of angles the prop upwards when I raise it.

 

[Kez]

If your K&B can turn the X450, that is good. I would start working on the set up.

 

[Sean Janne]

It was bogging down with the 2 blade 450, until some cup was taken out of it.

Is it safe to say that a 3 blade 450 is a good starting point for the CMB 45?

 

[Kez]

That did not surprise me. My K&B 7.5 could not turn the 450 neither. At your strut depth, it will only put higher load.

Your CMB45 will have lots more power. I would start with that and see if it can handle the prop. If not, I suggest to raise the strut to 1/2" or try at smaller prop at your current stut setting. X447 would be a good place to start.

 

[jeff baham]

sean, when you install your push rod to the rudder make sure it is straight as possible use 4-40 or 1/8 rod

 

[Sean Janne]

sean, when you install your push rod to the rudder make sure it is straight as possible use 4-40 or 1/8 rod

I'm working on installing a new pushrod that is straighter. Thanks!